System for conveying blanks to a blowing installation for containers

ABSTRACT

The invention relates to a system of conveyance for a blowing installation for thermoplastic containers, comprising a series of conveyor elements ( 24 ) which are fitted with a gripper device ( 26, 28 ), whereby each gripper device can move in an axial direction in relation to the conveyor element ( 24 ) on which it is borne in order to become axially engaged on the neck ( 12 ) of the blank ( 10 ). An external radial collar ( 14 ) enables said blank ( 10 ) to rest upon a bearing surface ( 23 ). The invention is characterized in that each conveyor element ( 24 ) comprises a stabilizer ( 34 ) which can move in an axial direction from a high retracted position to a low position in order to bear upon the blank ( 10 ) so that it can be pressed against the bearing surface ( 23 ) before the gripper device ( 26, 28 ) engages with the collar ( 12 ).

The invention relates to methods for manufacturing hollow thermoplasticobjects whereby in a first step, a blank is manufactured by injectionprior to obtaining the final container during a method comprising atleast one blowing step.

The blank obtained by injection usually has a tubular cylindrical bodythat is closed at one of its axial extremities and is extended at itsother extremity by a neck, also tubular. The neck is usually injected sothat it already has its final shape whereas in order to shape the finalcontainer, the body of the blank must undergo a rather significantdistortion following the blowing operation.

These methods relate in particular to the manufacture of polyethyleneterephthalate (PET) containers.

Several variants of these methods make up this family. Based on themethod used, the corresponding manufacturing installation comprises oneor several thermal conditioning ovens.

In all the methods in question, the blowing of the body of the blankrequires that the latter be brought to a temperature that is greaterthan the glass transition temperature of the material. With this end inview, the blank is subjected to thermal conditioning by having itcirculate inside an oven. The oven comprises heating means that are forexample made of infrared lamps in front of which the blank is movedusing a conveyor element. Advantageously, it is provided that the blankrotate on itself during while being moved in the oven.

The blanks are usually held on the conveyor elements by a gripper deviceconsisting of a mandrel that is engaged inside the blank's neck andholds the latter in place by tightening it against the inner face of theneck. However, in certain cases, the blank is gripped by the outer faceof the neck.

In some of these methods, we seek to increase the temperature hold ofthe final container's body by increasing the PET's crystallinity ratio.This is done by first subjecting the blank to a first blowing phase inorder to obtain an intermediate container that in turn is subjected to aheating phase in a thermal treatment oven, a phase during which itshrinks. This shrunken container is then subjected to a second blowingphase that gives it the shape of the final container.

In another method, the neck of the blank, the final container or anintermediate container is what we want to heat in order to increase itscrystallinity. Therefore, the installation comprises an adapted thermaltreatment oven.

In all cases, we see that the installations for the manufacture ofthermoplastic containers can comprise several types of thermal treatmentovens, where these ovens are of course adapted to the thermal treatmentthat is to be performed. However, all these ovens comprise a conveyorsystem.

These various systems are thus meant to convey objects that correspondto the various manufacturing phases of the final container. However,they are all conceived to seize this object by the neck, which does notundergo any basic geometric variation, even if certain treatments leadto a change in the structure of the material that constitutes the neck.Also, in the text that follows we will indifferently use the termpreform, blank or bottle to designate the object that is to be treatedin the oven.

According to a known technique, the conveyor system can for example becomprised of a conveyor link chain that moves continuously on itself.

To seize the preform, a conveyor element comprises a gripper device thatmoves in an axial direction in relation to the conveyor element andthat, when brought from an extreme cleared position to an extremegripping position, engages in an axial direction on the neck of theblank.

For this to take place, the blank must be brought under thecorresponding conveyor element and must be held directly above saidelement throughout the entire duration of the seizing operation. Yet,during this time, the conveyor element moves continuously, therefore,the blank must also be moved continuously.

With this end in view, the blank is for example supported by a loadingwheel that comprises a disk that is driven in rotation around its axisand is fitted, on its periphery, with notches that are more or lesssemi-circular. An arc of circle guide is arranged around a portion ofthe disk's periphery in such a way that a blank can be clasped in aradial direction between a notch of the disk and the guide. The blankthen rests by a collar located at the base of its neck on both the diskand the guide, where the neck and the body of the preform extendrespectively above and under the level of the disk. Thus, the preform iscarried by the loading wheel and, through the rotation of the disk, isdriven following a circular trajectory.

The loading wheel is arranged in such a way that the circular trajectoryof the preform is at a point that is at a tangent to the direction inwhich the conveyor system moves. The movements of the wheel and theconveyor elements are synchronized so that, at this point of tangency,the blank is arranged in an axial direction directly over the gripperdevice of one of the conveyor elements. Thus, at this point, the gripperdevice can be made to move towards its low position to seize the blankby the neck.

Therefore, we note that, at the point of tangency, the blank still restson the loading wheel and on the guide, which stops right after thispoint to allow the blank to follow its new trajectory, which is that ofthe conveyor element.

In theory, at the loading point level, the blank rests by its collar onthe loading wheel and its position is perfectly defined by the notch ofthe disk in which it is clasped.

However, in practice, it is necessary to provide for operatingclearances between the blank, the disk and the guide. Therefore, theblank has a certain range of movement in relation to said two elements.Yet, we noted that this range allowed the blank to vibrate on theloading wheel. This is particularly noticeable in high paceinstallations in which the speed of the blank's movements at the levelof the loading wheel is relatively significant. Said vibrations affectthe precision of the actual position of the blank's neck at the level ofthe loading point so that, in some cases, the gripper device and theneck are offset to the point of preventing the blank from being grippedcorrectly.

Therefore, the objective of the invention it to suggest means that makeis possible to ensure that the preform is perfectly stable when it isgripped by the conveyor chain.

With this end in view, the invention suggests a system of conveyance forblowing installations for thermoplastic containers, of the type thatcomprises a series of conveyor elements fitted with at least one gripperdevice used to hold a container blank in order to move it along a pathinside the installation, of the type in which each gripper device movesin an axial direction in relation to the conveyor element that carriesit so that, when it is brought from a high cleared position to a lowgripped position, it engages in an axial direction with the blank'sneck, where the blank then rests by an external radial collar on abearing surface, characterized by the fact that each conveyor elementcomprises a stabilizer that can move in an axial direction from a highretracted position to a low position in order to bear upon the blank sothat it can be pressed against the bearing surface before the gripperdevice engages with the neck.

Based on other characteristics of the invention:

the stabilizer's movements between its high and its low positions arccontrolled by the movements of the gripper device;

the gripper device comprises a mandrel that engages in an axialdirection inside the blank's neck; the stabilizer comprises a bore whosediameter is more or less identical to the internal diameter of the neckand in which the mandrel can slide in an axial direction; and, in thehigh position, the mandrel is received inside the stabilizer whereas, inthe low gripping position, the mandrel extends outside the bore, througha lower opening delimited by the stabilizer's lower bearing edge;

at the beginning of its stroke toward its gripping position, the mandreldrives the stabilizer that comes to rest by its lower edge against thepreform in order to press it against the bearing surface; and themandrel continues its course until it reaches its gripping position;

during its return stroke toward its high cleared position, the mandrelbrings the stabilizer back toward its high retracted position;

the mandrel is received and tightened in the stabilizer's bore in such away that the mandrel drives the stabilizer by adherence;

the mandrel comprises a ring that is elastic in the radial direction sothat, in the mandrel's high position, it comes to rest against a lateralwall of the stabilizer's bore and, in the mandrel's low position, itcomes to rest against the inner surface of the blank's neck;

the gripping device and the stabilizer are connected in an axialdirection by elastic means;

the stabilizer slides in an axial direction in a tubular guide sheaththat is integral with the conveyor element, and

the stabilizer comes to rest on the upper edge of the blank's neck;

The invention also relates to a thermal conditioning oven for a blowinginstallation for thermoplastic containers, characterized by the factthat it comprises a system of conveyance that incorporates any one ofthe previous characteristics.

Other characteristics and advantages of the invention will becomeapparent after reading the following detailed description and looking atthe attached drawings where:

FIG. 1 is a perspective schematic view of an example of execution of themeans for transferring the preforms towards a system of conveyance asset forth in the invention; and

FIGS. 2 through 4 illustrate a conveyor element fitted with a preformstabilizer consistent with the invention, where the gripping device isillustrated in the high cleared position, in an intermediatestabilization position and in its low gripping position respectively.

The invention will now be described in the particular case of a systemof conveyance for a thermal oven that treats thermoplastic preforms 10,for example PET preforms. The preform 10 is made using molding byinjection and has a neck 12 that is shaped directly into its finalshape, where the neck comprises, at its base, an external radial collar14. In order to make the description clearer, we will assume throughoutthe remainder of the text that the preform 10 is arranged vertically,with the neck toward the top, as illustrated in FIGS. 1 and 2. Thegeometric terms used to describe the invention stem from this agreementand must not be considered as limitations to the scope of the invention.

In FIG. 1 we have illustrated a loading wheel 16 that is an example ofexecution of the transfer means used to bring the preforms to thethermal conditioning oven in a blowing installation for containers. Thisexample does not limit the scope of the invention. The loading wheel 16comprises a horizontal disk 18 that is driven in rotation at a constantspeed around its axis A0 and is fitted, on its external periphery, withnotches 20 that are more or less semi-circular. An arc of circle fixedguide 22 is arranged around a portion of the periphery of the disk 18.The disk and the guide are separated in a radial direction by a distancethat is more or less equal to half the diameter of the body of thepreform below the collar 14.

The performs 10 will each be engaged by feeding means (not represented)into a notch 20 of the disk 18, right in front of the beginning of thearc of circle guide 22. Therefore, the preform is driven by the notch 22and then becomes clasped in a radial direction between the disk 18 andthe guide 22 following a circular trajectory around the axis A0. Allalong this trajectory, the preform 10 rests by its collar 14, under thesole effect of its weight, on the disk 18 and the guide 22 that form abearing surface 23.

Thus, the loading wheel transfers the preform 10 to a loading pointwhere the trajectory of the preform on the loading wheel is more or lesstangential to that of the conveyor elements of a system of conveyance.The preform 10 is then under one of the conveyor elements 24, along thesame axis A1 as the latter.

The system of conveyance could for example be comprised in a known wayof a link chain, where for example each link carries one or two conveyorelements. However, the invention could apply to any similar system thatensures the conveyance of a container blank in a blowing installationfor containers from a previously injected preform. In particular, we canplan to have the conveyor elements laid out on a rotary crown or set upin the form of independent carriages.

From the point of tangency that corresponds more or less to an extremityof the guide 22, the conveyor element 24 loads the preform 10 so that,in this case, it will follow a path inside the oven.

FIGS. 2 through 4 illustrate three steps of how the conveyor element 24grips the preform 10.

As can be seen in these schematic figures, the conveyor element 24comprises a gripper device 26 that moves in an axial direction between ahigh cleared position and a low gripping position in which it is engagedwith the neck 12 of the preform 10. In the example shown, the gripperdevice 26 comprises, on its lower extremity, a mandrel 28 that will beengaged through tightening inside the neck 12. The mandrel 28 comprisesa ring 30 that is received in an annular groove made in the externalcylindrical surface of the mandrel 28. An elastomeric o-ring 32 isclasped in a radial direction between the ring 30 and the bottom of thegroove, so that the sections of the ring are solicited in a radialdirection toward the outside. Thus, when the mandrel 28 is in the lowposition inside the neck 12, the sections of the ring 30 rest on theinternal cylindrical surface of the neck 12, which holds the preform 10on the gripper mandrel 28. The ring 30 can also be made in the shape ofa split annular ring.

As set forth in the teachings of the invention, the conveyor element 24comprises a stabilizer 34 that moves in an axial direction to come andrest on the preform 10 before the mandrel 28 is engaged with the neck12. The stabilizer 34 is made in the shape of a tube element mounted asa slide in a tubular guide sheath 36 that is fixed in relation to a mainbody 38 of the conveyor element 24. The guide sheath 36 is of courseopen at its lower extremity. The stabilizer's lower extremity forms anannular edge 40 whose dimensions correspond with the upper edge 42 ofthe neck 12. This upper edge 42 is the edge that will delimit theopening of the final container.

In FIG. 2, the stabilizer 34 is illustrated in a high retracted positionin which it rests by its upper extremity against the fixed body 38 ofthe conveyor element 24.

The stabilizer 34 has an internal cylindrical bore that is open towardthe top and the bottom and in which the mandrel 28 is received withpossibility of a slide. The diameter of the bore is more or less equalto the internal diameter of the neck 12.

In the high position illustrated in FIG. 2, the mandrel 28 is fullyreceived inside the stabilizer's 28 bore so that its ring 30 rests in aradial direction against the stabilizer 34, which therefore creates asource of friction between the two.

Thus, when the mandrel is moved toward the bottom by its actuating means(not represented), it takes the stabilizer 34 with it in the directionof the preform, until the lower edge 40 of the stabilizer comes to restagainst the upper edge 42 of the neck 12 as represented in FIG. 3.

If the preform 10 rests by its collar 14 on the bearing surface 23, thestabilizer 34 is blocked in the axial direction. However, the mandrel 28can continue its course toward the bottom, where its ring 30 slides onthe internal cylindrical wall of the stabilizer 34. This slidingproduces a friction force that solicits the stabilizer toward thebottom, where in turn the stabilizer exerts a bearing force on thepreform's neck. This bearing force makes it possible it eliminate anypossibility of vibration of the preform, which guarantees a stable andperfectly defined position before the mandrel penetrates inside theneck.

In FIG. 4, we can see that, once the preform is stabilized, the mandrel28 can exit toward the bottom outside the stabilizer so as to penetrateinside the neck, where the ring 30 then cooperates with the internalsurface of the latter to make the preform integral with the conveyorelement 24.

Once the mandrel is engaged with the neck, the preform 10 can beevacuated from the loading wheel 16 using the system of conveyance asthe preform no longer has to be supported by its collar.

To unload the preform from the conveyor element, two options areavailable.

Thus, we can seize the preform by the neck, for example using eithertongs or a retaining surface that would cooperate with the upper surfaceof the collar 14, and order the mandrel 28 toward the top in order tofree it from the neck. In this case, once the ring 30 is out of theneck, it once again cooperates with the stabilizer so as to bring itback toward it high retracted position. In the retracted position, thestabilizer is immobilized in an axial direction toward the top againstthe body of the conveyor element and the mandrel can continue itsfreeing movement toward the top by penetrating inside the bore made inthe stabilizer.

In this way, we can also plan to have the stabilizer perform theejection function at the time of the unloading. In this case, we orderthe mandrel toward its high position. The preform, which is not heldback, follows the movement of the mandrel causing the stabilizer to moveupward to its retracted position in which it rests against the body 38of the conveyor element 24. From this position, the preform can nolonger more upward so that the mandrel, which follows its course towardsits retracted position, exits the neck of the preform and thenpenetrates into the stabilizer's bore.

In the method of execution of the invention that has just beendescribed, we note that the stabilizer's movements are caused by themovements of the mandrel 28, without the intervention of any otherelement.

However, in an alternative method of execution (not represented), we forexample plan to have the mandrel order the lowering of the stabilizerusing a compression spring that is interposed in an axial directionbetween the two. In this case, when the stabilizer comes in contact withthe preform, the spring is compressed, which creates a bearing effortthat is transmitted by the stabilizer to the preform. With such a methodof execution we must however be careful to choose a spring whosestiffness is not too significant. Indeed, when the preform is clearedfrom the bearing surface 23, the spring continues to force an axialeffort toward the bottom on the preform. If the spring is too stiff,this effort could make the preform slide in relation to the mandrel,which would result in the preform having a bad axial position or evenbeing dropped.

As a variant, we could also plan to have the stabilizer come to rest onthe preform's collar 14.

In all cases, we would see that the effort exerted by the stabilizer onthe preform be relatively weak so as not to mark the preform. Thiseffort will have to be just sufficient enough to avoid vibrations of thepreform.

We will note in the method of execution described above that converselythe stabilizer no longer exerts any effort on the preform once the ring30 cooperates with the neck 12 and not with the stabilizer.

Therefore the invention makes it possible to guarantee perfectreliability of the preform loading operation on the system ofconveyance, even for the high pace machines in which speed of movementof the parts is important.

What is claimed is:
 1. System of conveyance for a blowing installationfor thermoplastic containers, of the type that comprises a series ofconveyor elements (24) fitted with at least one gripper device (26, 28)conceived to carry a blank (10) of the container in order to make itcirculate along a path inside the installation, of the type in whicheach gripper device (26, 28) moves in an axial direction in relation tothe conveyor element (24) that carries it so that when it is broughtfrom a cleared high position to a low gripped position, it engages in anaxial direction with the neck (12) of the blank (10), where the blank(10) then rests by an external radial collar (14) on a bearing surface(23), characterized by the fact that each conveyor element (24)comprises a stabilizer (34) that moves in an axial direction from a highretracted position to a low position to come and rest on the blank (10)in order to press it against the bearing surface (23) before the gripperdevice (26, 28) engages with the neck (12).
 2. System of conveyance asset forth in claim 1, characterized by the fact that the movements ofthe stabilizer (34) between its high and its low positions arecontrolled by the movements of the gripper device (26, 28).
 3. System ofconveyance as set forth in claim 1 or 2, characterized by the fact thatthe gripper device (26) comprises a mandrel (28) that engages in anaxial direction inside the neck (12) of the blank (10), by the fact thatthe stabilizer (34) comprises a bore whose diameter is more or lessidentical to the inner diameter of the neck (12) and in which themandrel (28) can slide in an axial direction, and by the fact that, inthe high position, the mandrel (28) is received inside the stabilizer(34) whereas in the low gripping position, the mandrel (28) extendsoutside the bore, through a lower opening delimited by an upper bearingedge (40) of the stabilizer (34).
 4. System of conveyance as set forthin claim 3, characterized by the fact that, at the beginning of itscourse toward the gripping position, the mandrel (28) drives thestabilizer (34) which comes to rest by its lower edge (40) against thepreform (10) so as to press it against the bearing surface (23), wherethe mandrel (28) continues its course to its gripping position. 5.System of conveyance as set forth in claim 4, characterized by the factthat during its return course toward its high cleared position, themandrel (28) brings the stabilizer (34) back to its high retractedposition.
 6. System of conveyance as set forth in claim 3, characterizedby the fact that the mandrel (28) is received and tightened in the boreof the stabilizer (34) so that the mandrel (28) drives the stabilizer(34) by adherence.
 7. System of conveyance as set forth in claim 6,characterized by the fact that the mandrel (28) comprises a ring (30)that is elastic in relation to the radial direction that, in themandrel's (28) high position comes to rest against the lateral wall ofthe bore stabilizer (34) and, in the mandrel's (28) low position,against the inner surface of the neck (12) of the blank (10).
 8. Systemof conveyance as set forth in claim 2, characterized by the fact thatthe gripper device (26) and the stabilizer (34) are connected in theaxial direction by elastic means.
 9. System of conveyance as set forthin claim 1, characterized by the fact that the stabilizer (34) slides inan axial direction in a tubular guide sheath (36) that is integral withthe conveyor element (38, 24).
 10. System of conveyance as set forth inclaim 1, characterized by the fact that the stabilizer (34) comes torest on the upper edge (42) of the neck (12) of the blank (10). 11.Thermal conditioning oven for a blowing installation for thermoplasticcontainera, characterized by the fact that it comprises a system ofconveyance according to claim 1.